The HGH testing policy was agreed to as part of the NFL's new collective bargaining agreement, and the league notified the union it was ready to start collecting blood samples Monday.
But the NFLPA balked at implementing the anti-doping measure, only days after its officials met with members of Congress about implementing the new policy.
"We informed the NFL yesterday that absent a collective agreement on several critical issues, blood collection is not ready to be implemented on Monday," the NFLPA's statement said. "We have advised the players."
NFL spokesman Greg Aiello wrote on his Twitter account the league is "disappointed" in the union's response.
Aiello also said its stance is contrary to the terms of the labor deal.
"We know of no reason why these initial steps should not begin next week, and none has been identified by the union," Aiello said.